* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Microsoft YaHei', '微软雅黑', Arial, sans-serif;
    background-color: #000;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    color: #fff;
}

.container {
    width: 100%;
    max-width: 1200px;
    height: 90vh;
    background-color: #000;
    border-radius: 10px;
    box-shadow: 0 0 20px rgba(255, 255, 255, 0.1);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.header {
    padding: 20px;
    display: flex;
    justify-content: flex-start;
    align-items: center;
    border-bottom: 1px solid #333;
}

.navigation {
    display: flex;
    gap: 10px;
    margin-top: 20px;
    justify-content: flex-end;
}

button {
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    background-color: #333;
    color: white;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #555;
}

button#prevSentence,
button#nextSentence {
    background-color: #4CAF50;
}

button#prevSentence:hover,
button#nextSentence:hover {
    background-color: #45a049;
}

button:disabled {
    background-color: #222;
    color: #555;
    cursor: not-allowed;
}

button#prevSentence:disabled,
button#nextSentence:disabled {
    background-color: #222;
    color: #555;
    cursor: not-allowed;
}

button#showProgress {
    padding: 8px 15px;
    font-size: 14px;
}

.content {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 20px;
    position: relative;
}

.sentence {
    font-size: 36px;
    text-align: center;
    line-height: 1.5;
    max-width: 90%;
    word-wrap: break-word;
    margin-bottom: 40px;
}

.progress-indicator {
    position: absolute;
    bottom: 80px;
    font-size: 24px;
    color: #ccc;
    background-color: rgba(0, 0, 0, 0.8);
    padding: 5px 15px;
    border-radius: 20px;
    display: none;
    border: 1px solid #333;
}

.end-notification {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: rgba(255, 50, 50, 0.8);
    color: white;
    padding: 10px 20px;
    border-radius: 5px;
    font-size: 20px;
    display: none;
    z-index: 100;
}

@media (max-width: 768px) {
    .header {
        flex-direction: column;
        gap: 15px;
    }
    
    .sentence {
        font-size: 28px;
    }
}

@media (min-width: 1200px) {
    .sentence {
        font-size: 48px;
    }
}
